Shellac is a great finish. It dries fast and if used correctly, can build up a decent protective layer on wood very effectively. It is not resistant to water or alcoholic beverages as varnish or lacquer are, but it is very forgiving to apply. Perhaps more importantly — it keeps my students busy. This last point needs some clarification.
Towards the end of the trimester, when my 9th-grade students are ready to apply a finish on their box projects, shellac becomes an indispensable ingredient in maintaining a healthy teaching atmosphere. Finishes such as oil, oil-varnish, wipe-on varnishes and pure varnishes take time to dry, or more accurately, polymerized. That means, that if a student is applying a layer of one of these finishes at the beginning or the middle of class, they have nothing else to do until the end of class, as they need to let their project dry for a day. Sure they can begin a new project or help a friend (some do that) but others gravitate to what teenagers like to do best — chatting with their friends. There is nothing wrong with chit-chat, as long as it doesn’t disrupt the conduct of the class.
So, in order to keep my students busy during the whole class, I choose an evaporating finish whose drying properties will allow the students to stay with their projects and reapply a few more layers of shellac throughout the class. The alcohol from a thin layer of shellac evaporates rapidly, so by the time a student has rubbed or brushed a layer on the entire box and lid, they only need to wait a minute or so before repeating the process. I tell them that the thinner the layer, the better the finish is and the less likely it will be to attract contaminants such as dust and other airborne debris. I noticed that even the students who use a brush and apply coats of finish very generously, manage to apply a second or even third coat during the class. This technique keeps them productive and engaged in their project for most of the class.
Another advantage of Shellac is its forgiveness. By that, I mean that even an inexperienced student or a student who doesn’t have the highest level of patience will be able to achieve a decent outcome. I attribute the “forgiveness” characteristic to shellac’s ease of sanding between coats and the fact that if worse came to worst and a student created a finished surface that looked like the surface of the moon, we could dissolve and clean the entire finish with the help of denatured alcohol.
One last, but very important advantage of using shellac in the classroom is the subject of brush cleaning. No matter how much you emphasize the importance of thorough brush cleaning as the key factor in the longevity of a brush, you’ll always have one student who will forget or misunderstand the process. I have seen students who, after using an oil-based finish, skipped the mineral spirit “bath” and went straight to soap and water. In other cases, a student who just finished working with water-based polyurethane dunked his brush in mineral spirits. In other cases, the rinsing of solvent was not completed, or not enough attention was given to the shampooing of the brush at the end. In the days before we used shellac, we ended up with too many wasted brushes that could only be restored via a brush dissolving solvent and some elbow grease. With shellac things are completely different, as even if a student forgot to dunk and rinse the brush in our jar of alcohol at the end of the class, come next meeting the stiff bristles can be sprung back to normal after five minutes in the shellac container.
The bottom line is:
Nothing is worse than having your students unengaged during class. Shellac evaporates fast and is just waiting to be reapplied with minimal shortcomings and maximum forgiveness. Also, matter how much you beg your students to treat their brushes like the hair on their heads, some will mess up. So my advice to you is when teaching a group of teenagers, choose shellac as the go-to finish.
– Yoav Liberman